1. Field of the Invention
This invention relates to a method and an apparatus for supplying a coating material, in more particular, to a method and an apparatus for supplying a coating material which enable the dilution of a high-viscosity coating material to a suitable viscosity for coating and thereby the application of the same to an object to be coated.
2. Description of the Related Art
There have been known an apparatus for supplying a coating material in which two different types of liquid components are pumped to join each other, then mixed together in a mixing machine, and supplied to a coating machine such as a coating gun, as disclosed in, for example, Japanese Patent Laid-Open No. 6-294379. This apparatus for supplying a coating material is constructed so as to allow a lower-viscosity liquid component, which is inferior in pump efficiency, to be supplied under pressure by adopting a pressure tank as lower-viscosity liquid component supplying means, when the two liquid components have different viscosities, whereby the precision of the mixing ratio of the two liquid components is intended to be heightened.
The use of the above described apparatus for supplying a coating material, however, has given rise to a problem of making it significantly difficult to supply a coating material to a coating machine, depending on the types of coating materials.
For example, when using a high-solids-content coating material having a solids content as high as about 70 to 100%, the coating material is difficult to flow through the piping with an ordinary pump due to its high viscosity, which causes a problem of being unable to mix it with a dilution solvent to dilute it to a desired viscosity.
Therefore, when supplying a high-viscosity coating material which requires dilution, the coating material has been diluted with a dilution solvent to a suitable viscosity for coating in advance within a tank into which the coating material is filled.
However, diluting a coating material in advance within such a tank still gives rise to a problem of being likely to cause solid-liquid separation due to the sedimentation of the pigments and powders of the coating material within the tank as well as within the piping to a coating machine so that the coating material with a desired viscosity cannot be obtained. Furthermore, constantly stirring the coating material in the tank and allowing the coating material to flow through the piping so as to avoid solid-liquid separation also produce a problem of not only increasing running cost, but also causing pigment deformation and changes in particle size distribution, resulting in changes in pigment color with time.
Accordingly, the object of this invention is to provide a method and an apparatus for supplying a coating material which can ensure supply of a coating material to a coating machine without causing a problem of solid-liquid separation even when using a high-viscosity coating material.
The above described object of this invention is accomplished by a method for supplying a coating material which includes: a step of supplying a high-viscosity coating material from a coating material tank to a mixing machine; a step of supplying a dilution solvent from a solvent tank to the above mixing machine; and a step of mixing the high-viscosity coating material and the dilution solvent in the above mixing machine to supply the mixture to a coating machine, wherein the step of supplying a high-viscosity coating material to a mixing machine includes a step of supplying the high-viscosity coating material fed from the coating material tank under the pressure of compressed air to the above mixing machine while quantifying the flow rate of the same with a metering pump.
The above described object of this invention is accomplished by an apparatus for supplying a coating material which includes: a coating material tank for storing a high-viscosity coating material; a solvent tank for storing a dilution solvent; a mixing machine for mixing the high-viscosity coating material and the dilution solvent; a metering pump for supplying the high-viscosity coating material from the above coating material tank to the above mixing machine; and a solvent pump for supplying the dilution solvent from the above solvent tank to the above mixing machine, wherein the above coating material tank is a pressure tank which allows the high-viscosity coating material to be fed under the pressure of compressed air and the above metering pump supplies the high-viscosity coating material fed from the coating material tank under the pressure of compressed air to the above mixing machine while quantifying the flow rate of the same.